370 W. BLAXLAND BENHAM. 



in the longitudiual muscles of the body-wall. The " arciform 

 muscles" are coufined to those somites between the male pore on 

 Somite xv and the hinder end of the clitellum at Somite xxxvii, 

 and serve to produce during copulation the groove on the 

 ventral surface, along which the spermatozoa travel from the 

 male pore of one worm to the spermathecee (?) of the other. 



Now in Moniligaster, though we have no knowledge of 

 the mode of copulation, yet there can be little doubt that these 

 oblique muscles are connected with that process. By their 

 contraction they would raise the ventral surface of the body 

 between the male pores and the spermathecal pores, not, as I 

 believe, for the passage of spermatozoa, but to help in holding 

 the two worms together. 



The minute structure of the prostate of M. Barwelli^ has 

 been dealt with by Beddard in more than one contribution ; 

 in one of these (4, p. 121, pi. xii, fig. 11) he figures a trans- 

 verse section of this structure, and it will be convenient to 

 refer to this briefly before passing to a consideration of what 

 I find to be the condition in the present species. In M. 

 Barwelli, then, the cavity of the prostate (or atrium) is lined 

 by columnar granular cells; outside this is a layer of muscles; 

 this, again, is surrounded by " an external covering composed 

 of large granular cells, which are separated into groups by 

 partitions. Each cell is prolonged into a fine process, which 

 extends at least as far as the muscular wall ; indeed, it is 

 difficult to believe that the cells do not in some way or other 

 reach the lumen of the atrium, and there discharge their 

 glandular secretion.'^ 



In M. indie us the hemispherical glandular portion of the 

 atrium, which portion may be termed the prostate, has a 

 structure differing from that of the more compressed duct 

 leading to the external aperture. The latter is provided with 

 an irregular lumen, lined by a low columnar, non-glandular 

 epithelium, the nuclei of which are oval and occupy the 



' I shall use the word " prostate " to refer to the glandular wall of the 

 organ, the word " atrium " being employed for the chamber into which the 

 gland-cells and sperm-duct open. 



